Not Applicable
Not Applicable
1. Field of the invention
This invention relates to air ventilation control systems and particularly to air ventilation control systems that provide fresh makeup air in tightly insulated buildings.
2. Description of the Prior Art
In the past, air ventilation systems in buildings and homes were simple-one opened and closed windows to adjust the comfort ranges in the building. Today, heating and cooling systems are considerably more complex. This complexity has been exacerbated by the latest building specification that call for the so-called super insulating of homes and other buildings. While the use of super insulating techniques has improved heating and cooling efficiency, it has produced problems. Because they are tightly sealed against drafts, these homes generally contain twice the insulation required in prevailing building codes, along with double or triple glazed windows. The envelope of this type of home is completely encased in a polyethylene air/vapor barrier, and all of its windows and doors are fitted with special seals to prevent the escape of heated inside air and its subsequent replacement by cool outside air. The tight sealing of these structures prevents the natural exchange of stale inside air for fresh outside air, which leads to elevated indoor air pollutant levels.
To overcome these problems systems have been developed to bring fresh air into the conditioned space to replace the xe2x80x9cstalexe2x80x9d air in the space. The problem in doing this is that the fresh air being introduced is usually at a different temperature than that of the inside space. Thus, for cold climates, bringing in fresh air means bringing in colder air that takes energy to heat before it can be used. Similarly, in hot climates the opposite problem exists. To solve this problem, air-to-air heat exchangers and mixing dampers have been developed.
U.S. Pat. No. 4,044,947 to Spethmann teaches a control apparatus for controlling an outdoor air damper and a recirculated air damper of an air conditioning system for maintaining a predetermined condition, such as temperature, and a predetermined volume of the air to be discharged to the zones supplied by the air conditioning system. In this manner, separate volume control dampers may be eliminated by requiring the outdoor air and recirculated air mixing dampers to perform both the functions of controlling the condition of the mixture of outdoor air and recirculated air and controlling the volume of the mixture of air supplied to the zones.
The control apparatus may also use variable gain amplifiers connected to a temperature sensor, which senses the temperature of the mixed air, either upstream or downstream of the fan, and a second input connected to at least one volume sensor responsive to the volume of air moving through the system. The outputs from the variable gain amplifiers are connected to the appropriate outdoor air damper and/or recirculated air damper for regulating the condition and volume of the mixture of outdoor air and return air supplied to the zones. In this way, upon an increase in the static pressure in the system, the gain of the amplifiers is adjusted to reduce the volume of air supplied to the system by the outdoor air and recirculated air damper. The volume of the system return is regulated by the same type of exhaust and recirculating air dampers.
U.S. Pat. No. 4,776,385 to Dean relates to those devices for enabling and disabling heating and cooling equipment and providing supplemental ventilation to an enclosure. An air intake unit is ducted to a central heating and cooling installation. The intake fan unit has an outside temperature thermostat associated therewith and which is wired to a control circuit that also monitors temperature in proximity to a thermostat-equipped exhaust fan unit located in an attic or upper crawl space. Sensing devices are used in association with the plurality of thermostats to selectively enable or disable the heating and cooling equipment and to actuate the intake and exhaust fan units, thereby providing ventilation in the space.
U.S. Pat. No. 4,735,130 discloses a fresh air make-up apparatus for a furnace located in an enclosed building that comprises an elongated diffuser housing positioned adjacent the furnace, with the housing having an inlet in communication with fresh outside air and a pair of outlets, one being connected to the cold air return of a forced air furnace at a point substantially upstream of the heat exchanger, and the other outlet leading to the room. The outlet leading to the cold air return provides fresh make-up air for the building, while the opening leading to the room provides both a means for diffusing and preheating the fresh air supplied to the cold air return and a means for providing fresh air diffused with warm room air to the combustion chamber of the furnace. The apparatus also includes a removable filter for removing contaminants from the fresh air. The apparatus can include a heat exchanger for preheating the fresh air with warm air from the warm air duct of the furnace. This warm air is then exhausted outside the building to provide a continuous air exchange within the building. Although this system is simple, it merely adds air to the intake of a furnace. Without any systematic conditioning or operating parameters.
U.S. Pat. No. 5,082,173 to Poehlman et al. teaches a dynamic environmental control system for controlling the environment in a super insulated tightly sealed home which uses a heat recovery ventilator (HRV) connected to a forced air heating system for ventilation. The system performs a number of functions according to predetermined priorities. Firstly, for health reasons, the system will initiate an air exchange if HRV running times have been inadequate to ensure a minimum fresh air content and at the same time to dilute air pollutants which build up over time in an unventilated home. In addition, in order to minimize the effects of high humidity outputs caused by cooking, bathing, washing or drying, the system permits the user to initiate a timed HRV run to rid the home of the anticipated humidity. Such operations are special events that are activated over a background monitoring of inside temperature gradients that can be equalized by the system activating a forced air system whenever a preset maximum value is exceeded. The system may also function in one of its aspects as a seven day four temperature setback thermostat and is programmed to initiate an HRV run to remove humidity from a home if the humidity level is not within a desired range or if an inside dew point violation is likely; provided that the inside and outside moisture levels are favorable for removing humidity from the home. However, it is limited in that it is designed for use during the heating season when a heater and an indoor ventilation system are in use and when the windows are closed to seal in the environment in the home. The device is also restricted by climatic conditions in that it can only be used effectively in relatively dry climates where the moisture content of outside air is normally lower than the desired moisture content of inside air. For this reason the system is less suitable for use in areas that experience a regular extended rainy season of several weeks or more during the heating season. Moreover, the system uses complex electronic circuits that control the system. Such circuits are difficult to program and maintain.
U.S. Pat. No. 5,881,806 to Rudd discloses a system that is a fan recycling control system for using the existing air distribution fan and ducts of an air conditioning system, having heating and/or cooling and/or humidifying and/or dehumidifying operating modes. The system is designed for the periodic distributing of ventilation air and mixing of air throughout the interior air space served by the air conditioning system during periods in which the air distribution fan is not operating due to lack of a positive signal from the thermostat for heating or cooling, or the humidistat for humidifying or dehumidifying, or constant fan modes. The fan recycling control provides a means for operating the air distribution fan for a first selectable time period after a second selectable time period from the end of the last operation of the air distribution fan, where the last operation of the air distribution fan could have been due to a positive signal from the thermostat or humidistat for heating or cooling or humidifying or dehumidifying or constant fan modes of the air conditioning system, or due to fan operation initiated by the fan recycling control. The system includes an outside air damper recycling control having a means to open a motorized outside air damper, for the purpose of drawing in ventilation air, each time the air distribution fan operates, and for as long as the air distribution fan continues to operate, having a means to cycle, periodically close then open, the outside air damper based on selectable time periods since it was last opened or closed, respectively, and having a means to cause the motorized outside air damper to close at the end of each operation of the air distribution fan. Although this system has many of the desired features, it has a complex set of controls to operate the system. This makes setting and operating the unit more difficult. For example, the control panel has three timers: one for fan off time, one for fan on time, and one for the damper cycle time. If any of these times are mis-set or not set, the system cannot function properly.
The instant invention overcomes these difficulties. It is a system that allows fresh air to be brought into a furnace as part of the return air circuit. This not only helps to replace stale air within a home, it also prevents air infiltration, around windows, doors, floor registers, and wall base perimeters. This occurs through normal use of bathroom and kitchen ventilation units, which cause periods of negative pressure with the dwelling. The hardware of the basic system consists of a furnace that has a return air supply duct, an intake louver and filter through which fresh air enters into the system, an intake fan mounted to the intake, an intake duct that brings the fresh air from the intake louver to the furnace and a motorized damper, installed in the intake duct, to control the flow of air. These components are controlled by a control panel that works in conjunction with the thermostat and furnace controls to operate the intake fan and damper as needed and desired for optimum operation.
Specifically, the system is designed to control air recirculation and to introduce filtered fresh air into residential units at various times and for specific durations selected in a 24-hour period.
The system also:
a) shares control with the thermostat of a residential forced air furnaces;
b) initiates air recirculation at the times selected and for durations specified by the user;
c) operates in conjunction with or independent of heating or cooling cycles;
d) operates dampers and blowers to admit and control a flow of filtered fresh air through a duct tied into the return air plenum ahead of the furnace filter, to mix with the air circulated during periods of heating, cooling and recirculation;
e) operates heaters, in fresh air supply ducts, to pre-heat the incoming air during periods of extreme cold weather;
f) controls the blowers, in air-to-air heat recovery units, and associated damper networks-used for energy savings (regardless of climate) during make-up air supply, whether used in a residence with a forced-air heating/cooling system or one with a stand-alone recirculation/make-up air system;
g) can operate with unit controlled voltages of various magnitudes (e.g., 120 volts and below, either AC or DC, as dictated by voltage requirements of the components used);
h) can use differential pressure to establish the need for air intake;
i) can monitor for the presence of gases (e.g., carbon monoxide) to initiate air intake; and
k) can shut-down air intake and recirculation upon detection of smoke using either an in-duct mounted smoke detector or other smoke or heat detection devices equipped with the necessary switch or relay contacts to disconnect the power to the control circuits. Unlike the prior art systems, which solve one problem, this system is designed to work in a variety of ways to ensure that the flow of air into a home is maintained to provide the optimum level of comfort and safety.